704. 二分查找

 三种写法都过。

代码一：

1 class Solution(object):
2     def search(self, nums, target):
3         """
4         :type nums: List[int]
5         :type target: int
6         :rtype: int
7         """
8         if target in nums:
9             return nums.index(target)
10         else:
11             return -1

代码二：

1 class Solution(object):
2     def search(self, nums, target):
3         """
4         :type nums: List[int]
5         :type target: int
6         :rtype: int
7         """
8         i, j = 0, len(nums)-1
9
10         while i <= j:
11             mid = int((i+j) / 2)
12             if nums[mid] == target:
13                 return mid
14             elif nums[mid] < target:
15                 i = mid+1
16             else:
17                 j = mid-1
18         return -1

代码三：

1 class Solution(object):
2     def search(self, nums, target):
3         """
4         :type nums: List[int]
5         :type target: int
6         :rtype: int
7         """
8         i, j = 0, len(nums)-1
9         if i == j and nums[i] == target:
10             return i
11         while i <= j:
12             mid = i + int((j - i) / 2)
13             if nums[mid] == target:
14                 return mid
15             elif nums[mid] < target:
16                 i = mid+1
17             else:
18                 j = mid-1
19         return -1